Showing papers on "Interferometry published in 2011"
TL;DR: The device, termed a “coherent perfect absorber,” functions as an absorptive interferometer, with potential practical applications in integrated optics, and it is demonstrated that absorption can be reduced substantially by varying the relative phase of the incident fields.
Abstract: In the time-reversed counterpart to laser emission, incident coherent optical fields are perfectly absorbed within a resonator that contains a loss medium instead of a gain medium. The incident fields and frequency must coincide with those of the corresponding laser with gain. We demonstrated this effect for two counterpropagating incident fields in a silicon cavity, showing that absorption can be enhanced by two orders of magnitude, the maximum predicted by theory for our experimental setup. In addition, we showed that absorption can be reduced substantially by varying the relative phase of the incident fields. The device, termed a “coherent perfect absorber,” functions as an absorptive interferometer, with potential practical applications in integrated optics.
745 citations
TL;DR: An experiment determined the trajectories of single photons through a two-slit interferometer and reconstructed these trajectories by performing a weak measurement of the photon momentum, postselected according to the result of a strong measurement of photon position in a series of planes.
Abstract: A consequence of the quantum mechanical uncertainty principle is that one may not discuss the path or "trajectory" that a quantum particle takes, because any measurement of position irrevocably disturbs the momentum, and vice versa. Using weak measurements, however, it is possible to operationally define a set of trajectories for an ensemble of quantum particles. We sent single photons emitted by a quantum dot through a double-slit interferometer and reconstructed these trajectories by performing a weak measurement of the photon momentum, postselected according to the result of a strong measurement of photon position in a series of planes. The results provide an observationally grounded description of the propagation of subensembles of quantum particles in a two-slit interferometer.
624 citations
TL;DR: This work used spin dynamics in Bose-Einstein condensates to create large ensembles of up to 104 pair-correlated atoms with an interferometric sensitivity beyond the shot noise limit, and points the way toward a new generation of atom interferometers.
Abstract: Interferometers with atomic ensembles are an integral part of modern precision metrology. However, these interferometers are fundamentally restricted by the shot noise limit, which can only be overcome by creating quantum entanglement among the atoms. We used spin dynamics in Bose-Einstein condensates to create large ensembles of up to 104 pair-correlated atoms with an interferometric sensitivity − 1 . 61 − 1 . 1 + 0. 98 decibels beyond the shot noise limit. Our proof-of-principle results point the way toward a new generation of atom interferometers.
354 citations
TL;DR: The first operation of an airborne matter-wave accelerometer set up aboard a 0g plane and operating during the standard gravity and microgravity phases of the flight is reported.
Abstract: Inertial sensors relying on atom interferometry offer a breakthrough advance in a variety of applications, such as inertial navigation, gravimetry or ground- and space-based tests of fundamental physics These instruments require a quiet environment to reach their performance and using them outside the laboratory remains a challenge Here we report the first operation of an airborne matter-wave accelerometer set up aboard a 0g plane and operating during the standard gravity (1g) and microgravity (0g) phases of the flight At 1g, the sensor can detect inertial effects more than 300 times weaker than the typical acceleration fluctuations of the aircraft We describe the improvement of the interferometer sensitivity in 0g, which reaches 2 x 10-4 ms-2 / \surdHz with our current setup We finally discuss the extension of our method to airborne and spaceborne tests of the Universality of free fall with matter waves
352 citations
TL;DR: In this article, the authors measure the monochromatic transmission matrix (TM) of an optical multiple scattering medium using a spatial light modulator together with a phase-shifting interferometry measurement method.
Abstract: We experimentally measure the monochromatic transmission matrix (TM) of an optical multiple scattering medium using a spatial light modulator together with a phase-shifting interferometry measurement method. The TM contains all the information needed to shape the scattered output field at will or to detect an image through the medium. We confront theory and experiment for these applications and study the effect of noise on the reconstruction method. We also extracted from the TM information about the statistical properties of the medium and the light transport within it. In particular, we are able to isolate the contributions of the memory effect and measure its attenuation length.
249 citations
TL;DR: In this article, the amplitude and phase of ultrafast optical pulses with the aid of a synchronized incoherently related clock pulse were measured using a novel variation of spectral phase interferometry for direct electric field reconstruction (SPIDER) that exploits degenerate four-wave mixing.
Abstract: he recent introduction of coherent optical communications has created a compelling need for ultrafast phase-sensitive measurement techniques operating at milliwatt peak power levels and in timescales ranging from sub-picoseconds to nanoseconds. Previous reports of ultrafast optical signal measurements in integrated platforms include time-lens temporal imaging on a silicon chip and waveguide-based frequency-resolved optical gating (FROG). Time-lens imaging is phase-insensitive, and waveguide-based FROG methods require the integration of long tunable delay lines, which is still an unsolved challenge. Here, we report a device capable of characterizing both the amplitude and phase of ultrafast optical pulses with the aid of a synchronized incoherently related clock pulse. It is based on a novel variation of spectral phase interferometry for direct electric-field reconstruction (SPIDER) that exploits degenerate four-wave mixing in a CMOS-compatible chip. We measure pulses with a peak power of 1 THz, and up to 100 ps pulsewidths, yielding a timeg-bandwidth product of >100.
184 citations
TL;DR: Results from time-lapse investigations on living pancreas tumor cells demonstrate the capability of the Michelson interferometer approach for digital holographic microscopy for reliable quantitative phase contrast imaging.
Abstract: Many interferometry-based quantitative phase contrast imaging techniques require a separately generated coherent reference wave. This results in a low phase stability and the demand for a precise adjustment of the intensity ratio between object and reference wave. To overcome these problems, the performance of a Michelson interferometer approach for digital holographic microscopy was analyzed that avoids a separately generated reference wave by superposition of different image areas. It is shown that this simplified arrangement yields improved phase stability. Furthermore, results from time-lapse investigations on living pancreas tumor cells demonstrate the capability of the method for reliable quantitative phase contrast imaging.
182 citations
TL;DR: A cold-atom interferometers gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes and can be used for precise determination of latitude, azimuth, and Earth's rotation rate.
Abstract: We demonstrate a cold-atom interferometer gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes. We show how the instrument can be used for precise determination of latitude, azimuth (true north), and Earth's rotation rate. Spurious noise terms related to multiple-path interferences are suppressed by employing a novel time-skewed pulse sequence. Extended versions of this instrument appear capable of meeting the stringent requirements for inertial navigation, geodetic applications of Earth's rotation rate determination, and tests of general relativity.
180 citations
TL;DR: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber, which makes it very attractive for high-pressure and high-temperature sensing applications.
Abstract: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber. The photonic crystal fiber functions as a Fabry-Perot cavity and serves as a direct sensing probe without any additional components. Its pressure and temperature responses in the range of 0-40 MPa and 25°C-700°C were experimentally studied. The proposed sensor is easy to fabricate, potentially low-cost, and compact in size, which makes it very attractive for high-pressure and high-temperature sensing applications.
172 citations
TL;DR: In this article, the authors constructed an interferometer with parametric amplifiers as beam splitters, and they found that the fringe intensity depends quadratically on the intensity of the phase sensing field at high gain.
Abstract: We construct an interferometer with parametric amplifiers as beam splitters. Because of the gain in the parametric amplifiers, the maximum output intensity of the interferometer can be much bigger than the input intensity as well as the intensity inside the interferometer (the phase sensing intensity). We find that the fringe intensity depends quadratically on the intensity of the phase sensing field at high gain. This type of nonlinear interferometer has better sensitivity than the traditional linear interferometer made of beam splitters with the same phase sensing intensity.
170 citations
Patent•
26 Sep 2011TL;DR: In this article, a method of processing interferograms is provided based on homodyne filtering, and a method for generating a record of a material modification process using an interferometry output is provided.
Abstract: Methods and systems are provided for using optical interferometry in the context of material modification processes such as surgical laser or welding applications. An imaging optical source that produces imaging light. A feedback controller controls at least one processing parameter of the material modification process based on an interferometry output generated using the imaging light. A method of processing interferograms is provided based on homodyne filtering. A method of generating a record of a material modification process using an interferometry output is provided.
TL;DR: In this article, a displacement sensor with sub-nanometer resolution based on the fiber-optic Fabry-Perot interferometer is proposed, which is able to provide sub-nodes of up to 0.084 nm over a dynamic range of 3 mm.
Abstract: A displacement sensor with subnanometer resolution based on the fiber-optic Fabry-Perot interferometer is proposed. The Fabry-Perot cavity is formed between the fiber end face and a high reflectivity mirror, which effectively improved the contrast of the interference fringe. Meanwhile, since the measuring range and the demodulate resolution for Fabry-Perot sensor are difficult to be improved simultaneously, a novel demodulation method based on the combination of the Fourier transform method and the minimum mean square error estimation-based signal processing method has been presented, which is capable of providing subnanometer resolution and absolute measurement over a wide dynamic range. The experimental results show that the resolution of the sensor is up to 0.084 nm over a dynamic range of 3 mm.
TL;DR: In this article, a plasmonic Mach-Zehnder interferometer (MZI) is integrated with a microfluidic chip for ultrasound biosensing, which is formed by patterning two parallel nanoslits in a thin metal film, and the sensor monitors the phase difference, induced by surface biomolecular adsorptions, between surface Plasmon waves propagating on top and bottom surfaces of the metal film.
Abstract: We experimentally demonstrate a plasmonic Mach–Zehnder interferometer (MZI) integrated with a microfluidic chip for ultrasensitive optical biosensing. The MZI is formed by patterning two parallel nanoslits in a thin metal film, and the sensor monitors the phase difference, induced by surface biomolecular adsorptions, between surface plasmon waves propagating on top and bottom surfaces of the metal film. The combination of a nanoplasmonic architecture and sensitive interferometric techniques in this compact sensing platform yields enhanced refractive index sensitivities greater than 3500 nm/RIU and record high sensing figures of merit exceeding 200 in the visible region, greatly surpassing those of previous plasmonic sensors and still hold potential for further improvement through optimization of the device structure. We demonstrate real-time, label-free, quantitative monitoring of streptavidin–biotin specific binding with high signal-to-noise ratio in this simple, ultrasensitive, and miniaturized plasmoni...
TL;DR: The design and characterization of Si₃N₄/SiO₂ optical waveguides which are specifically developed for optical delay lines in microwave photonics (MWP) signal processing applications and the potential of the waveguide technology to be applied to construct compact on-chip MWP signal processors are reported.
Abstract: We report the design and characterization of Si3N4/SiO2 optical waveguides which are specifically developed for optical delay lines in microwave photonics (MWP) signal processing applications. The waveguide structure consists of a stack of two Si3N4 stripes and SiO2 as an intermediate layer. Characterization of the waveguide propagation loss was performed in race track-shaped optical ring resonators (ORRs) with a free-spectral range of 20 GHz and a bending radius varied from 50 μm to 125 μm. A waveguide propagation loss as low as 0.095 dB/cm was measured in the ORRs with bend radii ≥ 70 μm. Using the waveguide technology two types of RF-modulated optical sideband filters with high sideband suppression and small transition band consisting of an Mach-Zehnder interferometer and ORRs are also demonstrated. These results demonstrate the potential of the waveguide technology to be applied to construct compact on-chip MWP signal processors.
TL;DR: In this article, an all-fiber high-sensitivity temperature fiber sensor based on a Mach-Zehnder interferometer in standard single-mode fibers (SMFs) is described.
Abstract: An all-fiber high-sensitivity temperature fiber sensor based on a Mach-Zehnder interferometer in standard single-mode fibers (SMFs) is described. The interferometer consists of two concatenated waist-enlarged fusion bitapers which are fabricated simply by cleaving and fusion splicing. It is demonstrated that such an all-fiber Mach-Zehnder interferometer incorporates intermodal interference between the LP01 mode and a high-order cladding mode of LP07 mode. Its response to temperature is investigated and a high sensitivity of 0.070 nm/°C is obtained by a 7.5 mm interferometer. This simple, low-cost and easy-to-fabricate core-cladding modal interferometer with entire SMF-based structure also has great potential in diverse sensing applications.
TL;DR: In this article, a signal demodulation algorithm based on the cross correlation and mean square error (MSE) estimation has been proposed for retrieving the cavity length of EFPI.
Abstract: Pressure sensors based on fiber-optic extrinsic Fabry-Perot interferometer (EFPI) have been extensively applied in various industrial and biomedical fields. In this paper, some key improvements of EFPI-based pressure sensors such as the controlled thermal bonding technique, diaphragm-based EFPI sensors, and white light interference technology have been reviewed. Recent progress on signal demodulation method and applications of EFPI-based pressure sensors has been introduced. Signal demodulation algorithms based on the cross correlation and mean square error (MSE) estimation have been proposed for retrieving the cavity length of EFPI. Absolute measurement with a resolution of 0.08 nm over large dynamic range has been carried out. For downhole monitoring, an EFPI and a fiber Bragg grating (FBG) cascade multiplexing fiber-optic sensor system has been developed, which can operate in temperature 300 °C with a good long-term stability and extremely low temperature cross-sensitivity. Diaphragm-based EFPI pressure sensors have been successfully used for low pressure and acoustic wave detection. Experimental results show that a sensitivity of 31 mV/Pa in the frequency range of 100 Hz to 12.7 kHz for aeroacoustic wave detection has been obtained.
TL;DR: In this paper, an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO) is proposed, where one or three interferometers are simultaneously operated through the use of two or three satellites in formation flight.
Abstract: We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of \({<10^{-18}/\sqrt{{\rm Hz}}}\) in the 50mHz–10Hz frequency range, providing access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline \(({\lesssim100\,{\rm m}})\) atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.
TL;DR: A highly sensitive refractive index (RI) sensor based on three cascaded single-mode fiber tapers, in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor.
Abstract: We report a highly sensitive refractive index (RI) sensor based on three cascaded single-mode fiber tapers, in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor. Experimental results show that the sensitivity of the device is 0.286 nm for a 0.01 RI change, which is about four times higher than that of the normal two-cascaded-taper-based Mach–Zehnder interferometer. In addition, the sensitivity of the device could be enhanced by tapering a longer and thinner middle weak taper. Such kinds of low-cost and highly sensitive fiber-optic RI sensors would find applications in chemical or biochemical sensing fields.
TL;DR: This work demonstrated high-speed parallel phase-shifting digital holography and obtained images of the phase variation of air caused by a compressed gas flow sprayed from a nozzle and found the interesting phenomenon of periodic phase distributions.
Abstract: Parallel phase-shifting digital holography can obtain three-dimensional information of a dynamically moving object with high accuracy by using space-division multiplexing of multiple holograms required for phase-shifting interferometry. We demonstrated high-speed parallel phase-shifting digital holography and obtained images of the phase variation of air caused by a compressed gas flow sprayed from a nozzle. In particular, we found the interesting phenomenon of periodic phase distributions. Reconstructed images were obtained at frame rates of 20,000 and 180,000 frames per second.
TL;DR: An at-wavelength wavefront error sensing method based on x-ray interferometry and an in situ phase compensator mirror, which adaptively deforms with nanometer precision, were developed to satisfy the Rayleigh criterion to achieve diffraction-limited focusing in a single-nanometer range.
Abstract: We have constructed an extremely precise optical system for hard-x-ray nanofocusing in a synchrotron radiation beamline. Precision multilayer mirrors were fabricated, tested, and employed as Kirkpatrick–Baez mirrors with a novel phase error compensator. In the phase compensator, an at-wavelength wavefront error sensing method based on x-ray interferometry and an in situ phase compensator mirror, which adaptively deforms with nanometer precision, were developed to satisfy the Rayleigh criterion to achieve diffraction-limited focusing in a single-nanometer range. The performance of the optics was tested at BL29XUL of SPring-8 and was confirmed to realize a spot size of approximately 7 nm.
TL;DR: In this paper, an optimized setup for two-dimensional (2D) IR spectroscopy is described, which can be implemented at low additional cost and with standard optics in any laboratory equipped for femtosecond mid-IR Spectroscopy.
Abstract: We describe an optimized setup for two-dimensional (2D) IR spectroscopy, which can be implemented at low additional cost and with standard optics in any laboratory equipped for femtosecond mid-IR spectroscopy. An interferometer produces a pair of intense pump pulses, whose interferogram is simultaneously recorded and directly yields the relative phase needed for the calculation of absorptive 2D spectra. We analyze different sampling methods based on a realistic noise model and introduce fast population time modulation as an alternative to the use of choppers in the suppression of scatter. Signal levels are compared to those of a photon-echo setup.
Patent•
06 Dec 2011
TL;DR: In this article, a distributed optical fiber sensor for detecting one or more physical parameters indicative of an environmental influence on a sensor optical fibre, as a function of position along the sensor fibre, is described.
Abstract: There is described a distributed optical fibre sensor for detecting one or more physical parameters indicative of an environmental influence on a sensor optical fibre, as a function of position along the sensor fibre. The sensor uses probe light pulses of different wavelengths. At least some of the probe light pulses may also be of different pulse lengths. The relative phase bias between interferometric signals in backscattered probe light of different wavelength pulses may also be controlled.
TL;DR: Time-resolved three-dimensional observation with X-ray Talbot interferometry is demonstrated and dynamic observation of a living worm in three dimensions with a time resolution of 0.5 s is demonstrated.
Abstract: X-ray Talbot interferometry is attractive as a method for X-ray phase imaging and phase tomography for objects that weakly absorb X-rays. Because X-ray Talbot interferometry has the advantage that X-rays of a broad energy bandwidth can be used, high-speed X-ray phase imaging is possible with white synchrotron radiation. In this paper, we demonstrate time-resolved three-dimensional observation with X-ray Talbot interferometry (namely, four-dimensional X-ray phase tomography). Differential phase images, from which a phase tomogram was reconstructed, were obtained through the Fourier-transform method, unlike the phase-stepping method that requires several (at least three) moire images to be measured sequentially in order to generate one differential phase image. We demonstrate dynamic observation of a living worm in three dimensions with a time resolution of 0.5 s, visualizing a drastic change in the respiratory tract.
TL;DR: Combining the new algorithms for estimating the laser phase and updating C value, the paper finally presents a novel technique for displacement measurement with improved accuracy performance in contrast to existing techniques.
Abstract: Approaches that are, to our knowledge, novel, are proposed in this paper to improve the accuracy performance of self-mixing interferometry (SMI) for displacement measurement First, the characteristics associated with signals observed in SMI systems are studied, based on which a new procedure is proposed for achieving accurate estimation of the laser phase The studies also revealed the reasons for the inherent errors associated with the existing SMI-based techniques for displacement measurement Then, this paper presents a new method for estimating the optical feedback level factor (denoted by C) in real time Combining the new algorithms for estimating the laser phase and updating C value, the paper finally presents a novel technique for displacement measurement with improved accuracy performance in contrast to existing techniques The proposed technique is verified by both simulation and experimental data
TL;DR: In this paper, the role of the Coulomb-dominated interference in the interference of the Fabry-P\'erot interferometer was explored, and it was shown that Coulomb interactions couple the interfering edge mode to localized quasiparticle states in the bulk, whose occupation is quantized in integer values.
Abstract: We analyze interference phenomena in the quantum-Hall analog of the Fabry-P\'erot interferometer, exploring the roles of the Aharonov-Bohm effect, Coulomb interactions, and fractional statistics on the oscillations of the resistance as one varies the magnetic field $B$ and/or the voltage ${V}_{G}$ applied to a side gate. Coulomb interactions couple the interfering edge mode to localized quasiparticle states in the bulk, whose occupation is quantized in integer values. For the integer quantum Hall effect, if the bulk-edge coupling is absent, the resistance exhibits an Aharonov-Bohm (AB) periodicity, where the phase is equal to the number of quanta of magnetic flux enclosed by a specified interferometer area. When bulk-edge coupling is present, the actual area of the interferometer oscillates as a function of $B$ and ${V}_{G}$, with a combination of smooth variation and abrupt jumps due to changes in the number of quasiparticles in the bulk of the interferometer. This modulates the AB phase and gives rise to additional periodicities in the resistance. In the limit of strong interactions, the amplitude of the AB oscillations becomes negligible, and one sees only the new ``Coulomb-dominated'' (CD) periodicity. In the limits where either the AB or the CD periodicities dominate, a color map of resistance will show a series of parallel stripes in the $B$-${V}_{G}$ plane, but the two cases show different stripe spacings and slopes of opposite signs. At intermediate coupling, one sees a superposition of the two patterns. We discuss dependences of the interference intensities on parameters including the temperature and the backscattering strengths of the individual constrictions. We also discuss how results are modified in a fractional quantized Hall system, and the extent to which the interferometer may demonstrate the fractional statistics of the quasiparticles.
TL;DR: This work proposes and theoretically explore a realization of this system in the optical domain, using a combined Michelson-Sagnac interferometer, which enables a strong and tunable dissipative coupling.
Abstract: Dissipative optomechanics studies the coupling of the motion of an optical element to the decay rate of a cavity We propose and theoretically explore a realization of this system in the optical domain, using a combined Michelson-Sagnac interferometer, which enables a strong and tunable dissipative coupling Quantum interference in such a setup results in the suppression of the lower motional sideband, leading to strongly enhanced cooling in the non-sideband-resolved regime With state-of-the-art parameters, ground-state cooling and low-power quantum-limited position transduction are both possible The possibility of a strong, tunable dissipative coupling opens up a new route towards observation of such fundamental optomechanical effects as nonlinear dynamics Beyond optomechanics, the suggested method can be readily transferred to other setups involving nonlinear media, atomic ensembles, or single atoms
TL;DR: The method was to use the quadrature and in-phase components of the signal, after removing the mean of each, to find the phase, unwrap it, and convert it to a displacement measurement.
Abstract: Using continuous wave, 94-GHz millimeter-wave interferometry, a signal representing chest wall motion can be obtained that contains both the heart rate and respiration patterns of a human subject. These components have to be separated from each other in the received signal. Our method was to use the quadrature and in-phase components of the signal, after removing the mean of each, to find the phase, unwrap it, and convert it to a displacement measurement. Using this, the power spectrum was examined for peaks, which corresponded to the heart rate and respiration rate. The displacement waveform of the chest was also analyzed for discrete heartbeats using a novel wavelet decomposition technique.
TL;DR: In this paper, an optical fiber twist sensor is proposed by using solid core low birefringence photonic crystal fiber (LB-PCF)-based Sagnac interferometer.
Abstract: An optical fiber twist sensor is proposed by using solid core low birefringence photonic crystal fiber (LB-PCF)-based Sagnac interferometer. The twist effects on the fiber are theoretically analyzed. The results show that the dip wavelength of the transmission spectrum shifts with the twist angle with a high sensitivity and resolution of 1.00 nm/0 and 0.010 , respectively. The sensor is also insensitive to environmental temperature change with an ultralow thermal dependent coeffiecient of -0.5 pm/0C.
TL;DR: In this article, a three-wave Fabry-Perot interferometer (FPI) fabricated in a single-mode optical fiber by focused ion beam (FIB) milling was used for simultaneous measurement of temperature and water salinity.
Abstract: We report a fiber sensor for simultaneous measurement of temperature and water salinity. The proposed sensor structure is based on a three-wave Fabry-Perot interferometer (FPI) fabricated in a single-mode optical fiber (SMF) by focused ion beam (FIB) milling. The open cavity of the three-wave FPI was filled with water under test and used as the main sensing element and the lengths of the open and silica cavity were comparable. These features of the proposed sensor lead to three groups of interference fringes with distinct sensitivities in the wavelength domain with respect to the changes in both the water salinity and ambient temperature are obtained. Consequently, simultaneous determination of the ambient temperature and water salinity variations is achieved using the sensitivity matrix method.
TL;DR: In this paper, the authors used HARPS for seismology and used the PAVO beam-combiner at CHARA for interferometry on the star 18 Sco to compare the solar twins directly to the Sun.
Abstract: The growing interest in solar twins is motivated by the possibility of comparing them directly to the Sun. To carry on this kind of analysis, we need to know their physical characteristics with precision. Our first objective is to use asteroseismology and interferometry on the brightest of them: 18 Sco. We observed the star during 12 nights with HARPS for seismology and used the PAVO beam-combiner at CHARA for interferometry. An average large frequency separation 134.4 ± 0.3 μHz and angular and linear radiuses